A broadband seismometer typically requires an adjustable mass positioning apparatus operated by an electrical motor or a manually adjusted screw to position an inertial mass to a measurement null point to compensate for the inertial mass moving from the null point due to environmental changes or mis-calibration. Mass positioning apparatuses can be prone to jamming, and problems can be difficult to diagnose without disassembling the instrument to visually inspect the apparatus.
Mass positioning apparatuses operate within a defined range beyond which no further adjustment is possible, but such traditional apparatuses do not report position information of the apparatus relative to its operational range, and so the operator of the seismic sensor cannot readily know what further range of adjustment is available and whether the instrument is operating with sufficient margin to compensate for future expected environmental changes.
There is a need to provide mass positioning apparatuses that are more reliable, that report position information and other diagnostic information, and that can be realized relatively economically inside the seismic sensor without significantly increasing the volume of the sensor enclosure.